Early telephony systems had very modest needs for signaling. The two primary types of information carried by the systems, control signaling and user traffic, shared the same path or “channel,” and only one type of information was allowed on the channel at any one time. As technology advanced and the sophistication of services increased, telecommunications networks moved to separate control signaling and user traffic onto distinct signaling channels and bearer channels, respectively. This “out-of-band” signaling technique allowed the signaling channel to be optimized for signaling, and the bearer channel to be optimized per its requirements. In addition, the separation led to increased efficiencies. For example, a “thin” signaling channel could be maintained, while higher bandwidth bearer channels could be allocated on demand. In addition, control signaling could better be protected from end user manipulation, and more efficient management of the network, including error recovery, was made possible.
Current telecommunications networks are moving toward all-IP (Internet Protocol) implementations in which a SIP (Session Initiation Protocol), end-to-end, call control protocol is used to communicate call control information (e.g., information regarding establishing and releasing communications sessions, among other things). According to these implementations, SIP traffic and user traffic (e.g., voice, video and other traffic) use different IP ports. However, the SIP and user traffic streams often share the same physical path. In high bandwidth terrestrial networks, it is common to over-provision the bandwidth so that the two traffic streams will both meet their respective Quality of Service (QoS). However, such over-provisioning is not desirable in bandwidth-constrained wireless networks, particularly those that carry voice traffic. For example, interruptions in the flow of voice packets in order to send SIP messages may unacceptably degrade the user-perceived communications quality. In addition, causing higher priority SIP signaling to wait an indeterminate amount of time for a break in the voice traffic would be a non-robust solution.
Some current systems attempt to solve the problems discussed above by allowing user equipment (UEs) to create separate bearer streams for user traffic and call control signaling traffic. The call control signaling traffic is considered by the network as a “special” category of data for which a higher QoS is maintained by supporting delivery guarantee (e.g., retransmissions), implementing special routing and protections, and assigning a higher priority for the call control signaling traffic, for example. The UEs take advantage of the differences in the QoS maintained for the two types of streams. Although this method may be effective, it is highly dependent on the appropriate provisioning of UEs and the network to identify and maintain the QoS associated with the call control signaling traffic. Accordingly, cooperative agreements are necessitated regarding the characteristics and support of the call control signaling and bearer paths.
Trends in the commercial telecommunications industry indicate a movement towards more centralized management approaches to IP-based communications. Such trends are in conflict with allowing differential management between the call control signaling and user traffic paths at the UEs, as is implemented in current systems. Accordingly, what are needed are methods and apparatus for separating IP-based, call control signaling traffic from user traffic in wireless networks in a manner that is consistent with industry trends towards centralized management of the IP-based communications. Other features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.